Hearing loss is the most frequent sensory defect in humans. Congenital, perinatal or early onset hearing loss occurs in approximately 7 out of 1000 neonates in the United States. In 50% of these cases, a genetic contribution is known or suspected, the powerful molecular and genetic techniques available in mouse and zebra fish are useful model systems for studying the biology of hearing. The functional similarities between mouse and human audition make mouse a particularly attractive model for hearing loss observed clinically. In support of Users of mice to study auditory system function, Core D will provide expert mouse husbandry (receiving, setting up crosses, weaning, fostering, background transfers, etc), genotyping, and notification/delivery of requested mice to Users. Per diem charges for mouse care will be the responsibility of the User, provided that they have a funded project that includes support for mouse cage costs. To encourage innovative and new collaborative projects, we will provide per diem support for common control animals and for approved projects in funding transition. All services provided by Core D will be reviewed periodically to ensure quality and accessibility. The Genetics Core will provide services for a variety of Users. Efficiency of mouse care will be increased greatly by having centralized, expert mouse husbandry and genotyping. Users not proficient in mouse care will gain access the vast number of identified gene knockout mice and defined spontaneous mutants to further their research. Experienced mouse users will benefit from the familiarity of the Core staff with mouse behavior and care, providing better health and higher fecundity for their strains. Training in husbandry, genotyping, and behavioral characterization will be available to all Users and their lab personnel. To encourage interactions and new collaborations, information about the strains, techniques, and projects being pursued by all Users of the Core will be disseminated online and in Genetics Core User meetings.